The invention relates to grass trimmers and, more particularly, to a convertible cap and head system for a trimmer that enables it to be converted from its original cutting medium to an alternative cutting medium or tool by changing at the head area, and not by changing the entire lower boom as currently practiced.
Handheld grass trimmers, powered by gas and or AC/DC electricity, have been popular outdoor tools for trimming grass and weeds along a variety of edges and into terrain where conventional mowers cannot practically or easily reach. Since their inception in the early 70's, trimmers have been largely confined to trimming light weeds and grass with monofilament string or nylon line (and/or metal/brittle plastic blades for heavier vegetation) as the primary cutting system used. Because of the high speeds required to reach the low mass mono line's cutting capability, high operating stresses cause continual breakage and consequently, manual or mechanical replenishment systems are needed to continuously feed or replenish the cutting line. Over the years, there have been limited improvements, but no real solution to the highly frustrating issues caused by weak and overstressed line.
In addition to the heavy and cantilevered weight the operator has to carry and maneuver, the trimmer, for the most part, must be handheld by the operator for many reasons because hitting the ground causes added line stresses to ultimately cause line breakage. Hitting abrasive surfaces should be avoided because it accelerates wear and breakage; hitting rocks or loose impediments should be avoided where possible to minimize dangerous thrown objects; only to name a few. Therefore, grass trimmers had to be ‘hand held’ to maneuver above and around the obstacles and impediments.
There are times when the operator may prefer to rest the spinning head and extended cutting line directly onto the ground to cut closer, or to try to cut at a given height, or perhaps for weight relief, but a number of problems, in addition to those related above, emerge as a result. Such problems may include thrusting, scalping, and other such control issues, as well as rapid line wear and breakage. Additionally, the surfaces rubbing onto the abrasive ground cause wear to the bump knob systems to become inoperable as the bumping knob grinds away.
Needless to say, handheld trimming can be a frustrating process with ‘string’ or ‘flexible line’ being the number one problem users have faced since the inception of the ‘string’ trimmer. For years, users have been constantly seeking solutions, as many new and different developments have offered promise toward a solution, but to no avail, mono line problems still remain the major problem. So very often, users want to try different systems that promise even the slightest improvement. To install such new innovations, however, removal of the old system becomes the requirement before the new system can be tested on the user's trimmer, or such replacements may likely not be properly installed to maintain the operator protection systems originally built into the trimmer.
Different users have different preferences for different cutting systems. For example, they may be satisfied with the original mono system provided with the original trimmer from the manufacturer which may likely include a popular bump type line replenishment system. On the other hand, due to poor line life and bump head complexities, they may want to try new innovative cutting systems with their own specific advantages. In either case, each original system, more than likely, must be removed in total and replaced by the other. There are generally no interchangeable or commonly used component parts. The entire system needs to be removed to make room for the replacement system to be mounted to the trimmer's arbor. In most cases, removal of the existing system is required to further assure the cutting line plane regulations with respect to the rear grass shield to be maintained to ANSI safety specifications.
Converting from the common manufacturer's grass trimmer mono filament line heads presents a great challenge if the user wants to change to another cutting system. In many cases, the original heads are permanently affixed, making it impossible to remove the old head system to adapt another system. Even if the old system is removable, the degree of difficulty can be extensive. Some systems, for example, use extra fastening and securing means such as more permanent retainer rings while others have special uncommon reverse threading needed for self-tightening purposes on different rotational directions. For example, a counterclockwise rotating trimmer needs left hand threads for self-tightening; otherwise, it could easily unscrew itself during decelerations.
Further, when removing the old head, it is a requirement to hold or lock the arbor so the head can be unscrewed from the arbor threads. Some trimmers do not have a visible means to hold the arbor, while others simply cannot be removed. These complexities have discouraged many customers incapable or unwilling to perform the needed conversion, thus denying the option of the new innovation. This is a very real and broad problem which this technology addresses.
It is also worth noting that conventional monofilament line does not cut grass to ‘quality’ conditions. It mashes and rips grass blades only to become ‘sun brown’ at these frazzled tips. The mono cutting line also pushes air and grass down and away from the cutting lines.
There is a further developing need for this easier ‘conversion’ innovation with newer developing technologies such as the trimmer's ground supporting glider, which now levels the cut while sharp leading flexible blades cut cleanly as they also lift air which lifts grass to effectively aid in cleaner cutting and rotary mowing. See, for example, U.S. patent application Ser. No. 14/280,916, the contents of which are hereby incorporated by reference. Additionally, a whole new series of benefits of the glider and line blade technologies will be further enhanced or emphasized with the contribution from the subject convertibility art.